1. Field of Invention
The invention relates to near field communications (NFC), and more specifically to reducing the multi-protocol polling duration, and thereby power consumption, for a polling NFC device.
2. Related Art
Near field communication (NFC) requires that NFC devices be present within a relatively small distance from one another so that their corresponding magnetic fields can exchange information. Ranges of up to several centimeters (generally a maximum of 0.1 meter) are common for NFC devices. Typically, a first NFC device transmits or generates a magnetic field modulated with the information, such as credit information or ticket fare information. This magnetic field inductively couples onto a second NFC device that is proximate to the first NFC device. The second NFC device may respond to the first NFC device by transmitting or generating its own modulated magnetic field and inductively coupling this magnetic field to the first NFC device.
A NFC reader is a type of NFC device that is capable of operating in an initiator mode to initiate a communication with another NFC enabled device. A NFC tag is a type of NFC device that is capable operating in a target mode to respond to the initiation of a communication by another NFC enabled device. A NFC communicator is a type of NFC device that is capable of operating in the initiator mode or in the target mode and is capable of switching between these two modes.
In a conventional polling procedure, the NFC reader or the NFC communicator generates a magnetic field and probes the magnetic field for the NFC tag or another NFC communicator. The conventional polling procedure contemplates multiple technologies, including Type A technology, Type B technology, and Type F (FeliCa) technology. The differences between the different technologies include modulation methods, coding schemes, and protocol initialization procedures. An example of the conventional polling procedure is described in “NFC Forum: NFC Activity Specification: Technical Specification, NFC Forum™ Activity 1.0 NFCForum-TS-Activity-1.0,” published Nov. 18, 2010 (hereinafter the “NFC Activity Specification”), and “NFC Forum: NFC Digital Protocol: Technical Specification, NFC Forum™ Digital 1.0 NFCForum-TS-DigitalProtocol-1.0,” published Nov. 17, 2010 (hereinafter the “NFC Digital Protocol”), which are incorporated by reference herein in their entirety.
The conventional polling procedure requires the NFC reader or the NFC communicator to initially generate the magnetic field for between 5 ms and 20 ms, conventionally referred to as a guard time, depending on the type of tag technology being used. Generation of the magnetic field for a duration of the guard time can use a high amount of current, conventionally, up to 250 mA to generate the magnetic field. The guard time is required before transmission of a polling command for each type of technology −5 ms for Type A and as well as for B, and 20 ms for Type F.
What is needed is a method and an apparatus to probe the magnetic field for NFC devices of differing technology types which reduces the duration that the magnetic field that is generated before sending the polling command to decrease the amount of power consumed during the polling procedure.
The invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.